Differences between RS232 and RS485
I. Introduction to RS232 Protocol
The RS-232 interface conforms to the serial data communication interface standard established by the Electronic Industries Alliance (EIA). Its original designation is EIA-RS-232 (abbreviated as 232, RS232). It is widely used for connecting computer serial interface peripherals, connecting cables, and in mechanical, electrical, signal, and transmission processes.
The RS-232-C standard specifies data transmission rates of 50, 75, 100, 150, 300, 600, 1200, 2400, 4800, 9600, and 19200 baud per second.
RS232 Characteristics
RS-232 is one of the mainstream serial communication interfaces. Due to its early development, the RS232 interface standard inevitably had shortcomings, mainly the following:
- The interface's signal level was relatively high, easily damaging the interface circuit chip. Furthermore, because it was incompatible with TTL levels, a level conversion circuit was required to connect to TTL circuits.
- The interface used a common ground transmission method with one signal line and one signal return line. This common ground transmission was prone to common-mode interference, resulting in weak noise immunity.
- The transmission distance was limited, with a maximum transmission distance of approximately 15 meters.
II. Introduction to the RS485 Protocol
This standard, defined by the Telecommunications Industry Association and the Electronic Industries Alliance, states that communication networks using this standard can effectively transmit signals over long distances and in environments with high electronic noise. This standard allows for the connection of multiple transceivers, providing multi-station capability and facilitating the establishment of a device network.
RS485 Features
RS-485 is very convenient for multi-point interconnection, saving many signal lines. RS-485 applications can be networked to form a distributed system, allowing up to 32 drivers and 32 receivers to be connected in parallel. To address the shortcomings of RS-232, the new standard RS-485 has the following characteristics:
- It uses differential signals to effectively reduce noise interference and extend communication distance, up to 4000 feet (actually up to 3000 meters);
- it has a low interface level, making it less prone to damaging the interface circuit chip;
- and it is compatible with TTL levels, facilitating connection to TTL circuits.
III. Summary of the differences between RS232 and RS485
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